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winter more and more homeowners become interested in the subject of window
condensation. It's not a happy interest. It stems from bad experiences
with window condensation, which range from irritating to downright
may strike you as odd, but the growing condensation problems of the nation
are caused by progress. Yes, if you have trouble with window condensation
it's probably because you live in a "tight" modern home that you can heat
for a fraction of the money it takes to heat the house your parents lived
in. And your condensation problems also result from widespread use of
several labor saving appliances that make life easier than it used to be.
article explains the moisture problems of the "tight" home. It offers
suggestions for curing condensation problems in existing homes and provides
suggestions for you who are planning a home. You will build a "tight" home
and there are more things you can do to PREVENT excessive moisture when you
build, than can be done in a home where the problem already exists.
Causes "Trouble" Condensation?
little fog on the lower corners of your windows now and then probably
doesn't bother you and shouldn't. By the time you've thought about it a
second time it has usually gone away. What we're talking about is EXCESSIVE
condensation. Condensation that blocks whole windows with fog or frost.
Water that runs off windows to stain woodwork... or in serious cases even
damage the wallpaper or plaster. If you have this kind of condensation on
your windows, you have a good reason worry and a good reason to act.
Don't worry so much about the windows...where you can SEE the effect of
excess humidity. You should worry more about what excess moisture may be
doing elsewhere in your home. It may be freezing in the insulation in your
attic where it will melt and damage your plaster exactly like a roof leak
when warm weather comes. It may be forcing its way out through siding to
form blisters under your exterior paint. That means the most expensive kind
of a paint job.
natural and easy in such cases to blame the paint, or the insulation, or the
windows. But it's wrong to blame them. The real villain is invisible. Its
water vapor...too MUCH water vapor. The best and usually the ONLY way to
prevent this trouble is to get rid of excess water vapor. Once you've
installed modern high performance windows with insulated glass, there isn't
very much more you can do to the windows to stop condensation.
Humidity, water vapor, moisture, steam. They're all the same. They are all
one form of water. Humidity is an invisible gas. It is present in varying
quantities in nearly all air. THIS MOISTURE IN WET AIR TRIES TO FLOW TOWARD
DRIER AIR AND MIX WITH IT. Scientists describe this force as "vapor
pressure'. It is often a very powerful force indeed. It can act
independently of the flow of the air, which holds the moisture. Vapor
pressure can force moisture easily through wood, plaster, cement and brick.
Right through most of the materials we use to build our homes. That is
exactly what happens when moisture seeks to escape from the humid air
usually found inside your home to the drier winter air outside.
MORE Moisture Trapped in LESS Space
Certain building materials stop water vapor. Glass is one of these. Also
on this list are some varnishes, paints, tiles, plastics, wall coverings.
Vapor barrier insulation is designed specifically to stop the escape of
water vapor and protect the insulation in your walls from the ravages of
water. Increased use of these "moisture trapping" materials in the last few
years has created the modern "tight" home. Moisture created by bathrooms,
kitchens, laundries and occupants no longer flows easily to the outside.
Modern insulation and construction that keep cold air OUTSIDE also keep
moisture in; so, it is very easy to build up excessive and even harmful
moisture levels in such homes. AMERICAN BUILDER magazine calls the problem
a combination of many causes that build excessive moisture in the modern
First, more washing, more bathing, more showers, more appliances, more gas
furnaces--all pour more water vapor into homes than in former years. HEATING
& VENTILATING magazine provides builders with reference data on sources of
water vapor. For instance, cooking for a family of four adds 4 1/2 lbs. of
moisture a day to a house. Each shower contributes ½ lbs.; weekly laundry
30 lbs., human occupancy 6 to 9 lbs.; dishwashing 1.2 lbs.
this moisture MUST eventually escape from your home. So you see that the
modern family of four can easily release 150 pounds or more than 18 GALLONS
of water per week into the air in their home! And houses with no basements
have further moisture problems.
David Bareuther, Associated Press Building editor, sums up the problem of
reducing humidity this way. He says there are only three ways to reduce
CONTROLLING SOURCES OF HUMIDITY: For instance, venting all gas burners,
clothes dryers, etc., to the outdoors. Use of kitchen or bathroom exhaust
WINTER VENTILATION: Because outside air usually contains less water vapor,
it will dilute the humidity of inside air. This takes place automatically
in older houses through constant infiltration (leaking) of outside air.
HEAT: The process of heating your home will reduce the relative
humidity--providing it's DRY HEAT. IT will counterbalance most of all the
moisture produced by modern living. Now, before we summarize specific steps
for reducing humidity in your home, let's include some basic data about
RECOMMENDED MOISTURE. You can refer to it if you are inclined to test the
moisture levels in your own home.
Practical Steps to Control Condensation
Here, arranged from easy to more difficult, are the steps you should take to
reduce condensation on your windows.
Put on storm windows or double-glazing.
Shut off furnace humidifier and any other humidifying devices in your home.
Be sure that louvers in attic or basement crawl spaces are open and that
they are large enough.
Run kitchen or other ventilating fans longer and more often than has been
Open fireplace damper to allow easier escape for moisture.
Air out your house a few minutes each day. Air out kitchen, laundry and
bathrooms during use or just following use.
If troublesome condensation persists see your heating contractor about an
outside air intake for your furnace, about venting of gas burning heaters
and appliances; or about installation of ventilating fans.
the common remedies we suggest (number 1 through 5) don't work, you have a
serious condensation problem. Changes your heating contractor may recommend
to further reduce humidity in your home should not be very expensive.
Certainly they will be less expensive than a big paint job caused by
excessive water vapor!
see, the basic principle of reducing window condensation is extremely
simple. When there is too much condensation on your windows, it means that
humidity is too high in your home. You should take necessary steps to
reduce humidity until condensation disappears.
in practice, window condensation and reducing humidity may become very
complicated; because many entirely different conditions may affect the way
the condensation problem works out in different homes. Here are a few:
number and type of windows in the home.
type of double-glazing system on the windows.
heating system, hot air or water, perimeter or interior wall heating.
type of insulation, vapor barrier and ventilation.
type of soil and quality of drainage.
Because of so many variables, a condensation problem can sometimes be very
tough to solve. That's why we recommend that you put an expert to work on
your problem if the simpler steps to reduce humidity don't solve your
condensation problem. See your architect or your heating contractor first.
If they can't help, we suggest that you ask your general contractor or
lumber dealer to put you in touch with a qualified expert. They are
available both at engineering schools and from the staffs of heating,
insulation, wallboard or window manufacturers.
Before we leave the subject of reducing humidity, we would like to add the
following There are two causes of condensation, which are TEMPORARY. They
will disappear after a few weeks or at most a season of heating.
First, there is the moisture that comes from a new construction or
remodeling. There's quite a lot of moisture in the wood, or the plaster or
other building materials of a new home. When the heating starts. This
moisture will gradually flow out into the air in the home. Then it will
disappear and not cause any more trouble.
the same sort of thing happens in milder form at the beginning of each
heating season. During the summer, your house has absorbed some moisture.
After the first few weeks of heating, your home will be dried out and you'll
have less trouble with condensation.
While we have been discussing the control of condensation we've mentioned
just about everything except windows. There's a good reason. There just is
nothing much that can be done with windows to cut down condensation. As the
building experts have often pointed out, the windows are not to blame for
condensation. In the moisture content of the inside air, lies both the
cause and the cure.